Süleyman Güngör

A spectral nodal method for one-group X,Y,Z-cartesian geometry discrete ordinates problems

Abstract The solution of one-group discrete ordinates S N problems with linearly anisotropic scattering in x , y , z - cartesian geometry has been studied by using SGF-CN “spectral Greens function-constant nodal’ method, developed first by De Barros and Larsen (1990–1992) for one dimensional and two dimensional x , y - cartesian geometries. The solutions of S N transverse - integrated nodal equations in which only constant nodal volume leakage approximation is made, are obtained by a simple iterative algorithm. Finally, tabulated numerical results of average cell scalar fluxes are provided.

General Eigenvalue Spectrum in a One-Dimensional Slab Geometry Transport Equation

Abstract A general theoretical scheme for the evolution of a general discrete eigenvalue spectrum in a one-dimensional slab geometry neutron transport equation is described. To make a general procedure, we described the consistent scattering kernel. By using this scattering kernel, discrete eigenvalues are computed. Three methods are presented for the calculation of discrete eigenvalues, but the simplest one is chosen for the computation. Numerical results are presented in the tables. Results are discussed and compared with those already obtained using various methods available in the literature.

Thorium utilization in an unmodified pressurized water reactor

Abstract The use of Th in pressurized water reactor (PWR) with no modifications in core lattice parameters, leads to a core design having the following advantages in U utilization and safety over low enriched U (LEU) standard design: 1. (a) Reduce U ore demands to support a reactor over its life (30 yr) by as much as 32% of that of standard PWRs and separative work by 11%. 2. (b) There will be no more enhancement on safety limits. The consequences of transient and postulated accidents are therefore expected to be no more serious than those for these U for which safety requirements have been satisfied.

Cluster Ab Initio Calculations of the Shape of Local Potential Well and of Positions for Oxygen Atoms in PCN (C=Cd)

Potential relief and equilibrium positions for oxygen atoms in Cd--O--Nb, Cd--O--Cd and Nb--O--Nb chains are studied in Pb(Cd 1/3 Nb 2/3 )O 3 (PCN) and Ba(Cd 1/3 Nb 2/3 )O 3 (BCN). Total energy cluster calculations are performed using ab initio restricted Hartree-Fock method. The electron correlation contribution is calculated within Møller-Plesset method. It is revealed that in PCN the oxygen atoms in Cd--O--Cd and Cd--O--Nb chains move in multi-well potentials with four minima shifted transversely to fourfold [001] axis. Whereas the oxygen atom in Nb--O--Nb chain in PCN and all oxygen atoms in BCN move in single-well potentials.

UN Method For The Critical Slab Problem In One‐Speed Neutron Transport Theory

The Chebyshev polynomial approximation (UN method) is used to solve the critical slab problem in one‐speed neutron transport theory using Marshak boundary condition. The isotropic scattering kernel with the combination of forward and backward scattering is chosen for the neutrons in a uniform finite slab. Numerical results obtained by the UN method are presented in the tables together with the results obtained by the well‐known PN method for comparison. It is shown that the method converges rapidly with its easily executable equations.

Spectral Green's Function Method for Neutron Transport with Backward and Forward Scattering in 1‐D Slab and Spherical Geometry

In this work, a combination of forward and backward scattering is studied for the numerical solution of one‐dimensional neutron transport problems in a finite homogeneous slab and sphere. The scattering of the neutrons is assumed to be anisotropic for the slab and isotropic for the spherical geometry. Numerical solutions are carried out by using both the spectral Greens function (SGF) and the diamond‐difference (DD) methods to check the accuracy of the results. Calculated numerical results of cell‐edge scalar fluxes are presented in the tables.

Phase Transition and Energy Spectra of Some Ferroelectrics-Ferroelastics

We report the results of electronic structure calculations for several types of MoO4-clusters in the Gd2(MoO4)3 structure in ferroelectric and paraelectric phase by using cluster ab initio restricted Hartree Fock method. The results give a variational approximation to the ground state electron densities of these clusters within the framework of ab initio restricted Hartree Fock (RHF) MO LCAO method.

Polarization induced electronic processes in a quantum well

Analysis of the electronic states in two dimensional systems is of considerable interest for the exclusive use of 2D systems in microelectronic devices as well as for the close relation of this problem to investigations of the some quantum effects. In microelectronic devices, the coupling between the electron 2D subsystem and polarization (induced or spontaneous) is often effectuated by depositing a lattice on the surface of a film with the 2D gas. In this case, the electrons are subjected to an external (or internal) periodic potential, which makes it possible to investigate the electron spectrum in such system. In present paper, the spectrum of the electronic states in an infinitely deep two dimensional asymmetric potential well, where one wall is periodically rough, is investigated theoretically. It is shown that in non-Bragg type resonances arise in such well. The resonances occur in a wide range of energies, starting at values close to the bottom in each 2D sub-band. The resonance interaction splits the energy spectrum and results in the appearance of gaps, giving the electron spectrum a mini-band character. The properties of the electron gas vary substantially in accordance with the new characteristics of the spectrum.